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;----------------------------------------------------------------------------- 
; Copyright (C) 2001 CYGNAL INTEGRATED PRODUCTS, INC. 
; All rights reserved. 
; 
; FILE NAME : SPI_MODE0.ASM 
; DATE : 14 DEC 01 
; TARGET MCU : C8051F30x 
; DESCRIPTION : This is a function which implements a master SPI port on 
; the C8051F30x series of devices. The function can 
; be called from a C program with the following function 
; prototype: 
; 
; extern char SPI_Transfer (char); 
; 
; NOTES : Timing is as follows (Mode 0 SPI): 
; Parameter SYSCLKs 
; MOSI valid to SCK rising 2 
; SCK rising to MISO Latch 2 
; SCK falling to MOSI valid 5 
; SCK high time 5 
; SCK low time 7 
; 
;----------------------------------------------------------------------------- 
NAME SPI_MODE0 
?PR?_SPI_Transfer?SPI_MODE0 SEGMENT CODE 
PUBLIC _SPI_Transfer 
$include (c8051f300.inc) ; Include regsiter definition file. 
$include (SPI_defs.h) ; Include sbit definitions for SPI 
RSEG ?PR?_SPI_Transfer?SPI_MODE0 
_SPI_Transfer: 
USING 0 
MOV A, R7 ; Store passed variable in A 
MOV R7, #08H ; Load R7 to count bits 
RLC A ; Rotate MSB into Carry Bit 
SPI_Loop: MOV MOSI, C ; Move bit out to MOSI 
SETB SCK ; Clock High 
MOV C, MISO ; Move MISO into Carry Bit 
RLC A ; Rotate Carry Bit into A 
CLR SCK ; Clock Low 
DJNZ R7, SPI_Loop ; Loop for another bit until finished 
MOV R7, A ; Store return value in R7 
?C0001: 
RET ; Return from routine 
END ; END OF FILE